1. Field of the Invention
The present invention relates to non-aqueous inks with an extended cap-off time, in particular relating to an ink for writing, drawing, painting or marking.
2. Description of the Related Art
Extended cap-off time in the present context means that the ink in the writing or application utensil does not dry up even after longer intervals with an unsealed writing tip or with a removed protective cap. The proposed ink makes it possible that the writing or application device can be left open for longer periods of time, preferably several hours or days.
Such inks are known in principle. In DE 196 26 824 C2 marker inks are employed with a cap-off additive, wherein the cap-off additive is present in the form of an insoluble paraffin wax and/or polyolefin wax in organic solvents. A good cap-off time of the marker is attained in this way.
However, it is disadvantageous that the cap-off effectiveness is not sufficient for application in holders with a fine line thickness.
To achieve an acceptable cap-off time in holders with a fine line thickness the paraffin content can be increased which however is effected at the cost of the downstroke that becomes very cloudy. In order to effectively use the parrafins/polyolefins also in fine line thicknesses without increasing their content, a very complex ink production procedure must be carried out.
Further marker inks are known which have a modified triglyceride as a cap-off additive. The disadvantage of using such cap-off additives is that the cap-off effectiveness is significantly inferior to that of inks with paraffin as a cap-off additive. Especially for inks with a high solid content, such as for example light-fast inks and overhead inks with luminous color, sufficient cap-off times were not achieved using these additives.
Monoesters of 2,2,4-Trimethyl-1,3-pentandiol diisobutyrate (TXIB) are also known as cap-off additives.
This additive which belongs to the group of plasticizers has a relatively high boiling point which can lead to a certain protection against drying. However, it is considered disadvantageous in this regard that the additive has a relatively high boiling point which, according to TXIB and literature, is at 244° C.; Inks with such an additive that have a good cap-off time also have a very high plasticizer content. The downstrokes of these inks dry only very slowly and are strikingly bad in terms of bonding strength. All in all, it is considered disadvantageous that a cap-off time is attained at the cost of bonding strength.
Moreover, a marking fluid is know from the publication JP-P/AS 1-35028 B2 to which a solid paraffin wax is added at room temperature that then dissolves completely in the organic solvent. It is considered disadvantageous that the employed solvents are no longer used in inks due to their physiology and covalent properties. Examples include chloroform, diethyl ether and benzine.
In comparison, an ink with an increased cap-off time is described in JP-P/AS 6-47 660 which can be left for longer periods of time without a protective cap. This ink consists of a colorant, an organic solvent, resin, decaglycerin and a-olefin (alpha-olefins). Olefin is the group designation for acyclic and cyclic aliphatic hydrocarbons with one or more reactive double bonds in the molecule.
When containing a-olefins the double bond is located between the first and second carbon atoms and is very reactive due to its unsaturated nature.
The presence of a-olefins in this ink is disadvantageous since it can render the ink unstable for storage due to reactions of the a-olefins with other ink components.